Polymyositis is a rare collagen disease that can involve the lungs. Between 5% and 30% of patients with polymyositis present interstitial lung disease at diagnosis or during the course of disease. Onset is usually insidious and involves dyspnea and nonproductive cough. Several histopathological findings are associated with polymyositis and the most common is nonspecific interstitial pneumonia. The prognosis of interstitial lung disease associated with polymyositis is better than that of idiopathic pulmonary fibrosis, since most patients respond to treatment with corticosteroids and immunosuppressants. We report the case of a 60-year-old woman with dyspnea and muscle weakness who was diagnosed with polymyositis and interstitial lung disease (radiography indicated possible nonspecific interstitial pneumonia). The patient responded well to prednisone and methotrexate.